1. Statement of the Technical Field
The inventive arrangements relate to antennas for radio communication equipment, and more particularly to rapidly deployable antennas used in high frequency radio communication systems.
2. Description of the Related Art
It is well known that HF frequencies present a key advantage to operators in a field environment, giving them the ability to achieve beyond-line-of-sight communications using the ionosphere, without depending on satellite availability or repeater infrastructure. However, depending on multiple variables including the current solar cycle, time of day, time of year, and distance and global position of desired communication link, only certain frequencies may be available to use. Particularly in the case of low-HF frequencies, antennas with good radiating performance tend to be physically very long, and for satisfactory performance may need to be elevated to a height that is difficult, inconvenient, and/or time-consuming to achieve by conventional means. In fact, in many scenarios Low-HF (<10 MHz) frequencies may be the only practical option available to support communications. For example, this is often the case during periods of low solar cycle activity, or at certain hours of the day. Also, if the desired distance for a communication link is in the 30-500 mile range, the lower end of the HF frequencies can be the only ones usable for operations in a near vertical incidence sky-wave (NVIS) mode.
Due to the long wavelengths, low-HF resonant dipole antennas are physically large and take time to deploy. Accordingly, antennas suitable for these types of communications present challenges to a field operator who is on the move. This can be especially true when the maximum usable frequency is less than 4 MHz. In such scenarios, the length of a resonant dipole becomes greater than 120 feet long, and a reasonable height above ground for efficient operation can be a minimum of 20 or 30 feet high.
In order to accommodate such antennas, telescoping masts and guy wires are often needed to achieve the required heights above ground for an antenna to be adequately efficient. Another often used method is to use trees, buildings, fences, or other tall-standing existing supports as they can be found in the field. Most cases require the use of an automatic antenna tuner to accommodate electrical lengths that are not resonant. This has an associated amount of loss in signal power.
To set up a reliable HF antenna that is usable in the low-HF frequencies of below 4 MHz is often time consuming to deploy, and to take down, and may contribute to a tactical decision to not take the time to set it up at all in the first place. If UHF and VHF communications are not possible due to non-line of sight, and HF equipment is not utilized, SATCOM channels are usually used, which are expensive, limited, and available bandwidth and channels are shared by many users.